Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Land	$ 59.0	$ 57.0
Premises	229.0	231.0
Equipment	344.0	311.0
Finance leases	11.9	0.0
Premises and equipment, gross	644.0	599.0
Accumulated depreciation	(299.0)	(267.0)
Total premises and equipment, net	$ 345.0	$ 332.0

Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing.

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Amount, after accumulated amortization, of right-of-use asset from finance lease.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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Amount before accumulated depreciation of tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.

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Amount of accumulated depreciation and amortization from plant, property, and equipment and right-of-use asset from finance lease.

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Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

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